Stainless Steel Seamless Pipe Rust

We need to carefully choose the most appropriate grade for stainless steel seamless pipe for a given application. In addition to careful material grade selection, good details and workmanship can significantly reduce the likelihood of contamination and corrosion.

Pitting
Pitting is likely to occur due to exposure to specific conditions, most notably the local form of the results that contain chlorides. In most structural applications, the degree of pitting is likely to be superficial, and the reduction in parts of a component is negligible. However, corrosion products pollute the architectural features. Pitting the intolerance of the service, such as pipes, pipes and containment structures, are passed. If there is a danger of a known pitting, then the molybdenum stainless steel bearing is required.

Crevice corrosion
Crevice Corrosion is a localized form of attack that is initiated by the extremely low availability of oxygen in the stone seam. It is only possible that in the stagnant solution, where the accumulation of chloride, may occur problems. The severity of crevice corrosion is very dependent on the geometric shape of the gap; narrower (about 25 microns) and deeper cracks, the more severe the corrosion. The cracks usually occur between the nut and the gasket or the rod or screw around the screw. The cracks can also occur in the weld but fail to penetrate and deposit on the steel surface.

Bimetallic (electric) corrosion
Bimetallic (electric) corrosion may occur in different metals in a common electrolyte contact (eg rain, condensation, etc.). If the current flows between the two, the less precious metal (anode) corrosion takes place at a faster rate than if the metal is not in contact.

The rate of corrosion also depends on the relative area of the metal in the composition of the temperature and electrolyte at the time of contact. In particular, the larger the cathode relative to the anode area, the greater the rate of attack. The unfavorable area ratio is likely to happen with the fastener and in the joints. Stainless steel components in carbon steel bolts should be avoided because the proportion of stainless steel carbon steel area is large and the bolts will be attacked attack. Conversely, the attack of carbon steel parts through a stainless steel bolt is much slower. It is usually helpful in taking advantage of previous experiences on similar sites because of the fact that different metals can often be safely accidentally condensed or moistened without adverse effects under conditions of coupling, especially when the electrolyte is low in conductivity.

The prediction of these effects is difficult because the corrosion rate is determined by a number of complex problems. The use of latent tables ignores the presence and area ratio of surface oxide films and the effects of different solutions (electrolytes) on chemistry. Therefore, do not understand the use of these tables may produce the wrong results. They should be used with caution and only for preliminary assessment.

Austenitic stainless steel are generally formed in bimetallic couple cathodes and are therefore not subject to corrosion. Austenitic stainless steel and zinc or aluminum contact may cause some additional corrosion in the latter two metals. It is less likely to be structurally significant, but the resulting white / gray powder can be considered unsightly. Bimetallic corrosion can be prevented by or from the details of the water that can be prevented or isolated from each other (for example, by drawing a different metal contact surface) (by painting or tape attached to the assembly joint EG). Insulation around the bolts can be achieved by nonconductive plastic or rubber washers and nylon or polytetrafluoroethylene gaskets and bushings. The system is a time-consuming detail that makes it at the scene, it is impossible to provide on-site inspection of the necessary scale to check all the washers and sleeves that have been properly installed.

Stress Corrosion Cracking (SCC)
Stress corrosion cracking (SCC) requires simultaneous tensile stress and specific environmental factors. It is rare in the normal building environment. The stress does not require very high relative to the elastic stress of the material and may be due to loading and / or manufacturing processes such as welding or bending residual effects. When containing high residual stress stainless steel members (eg, due to cold working) for chlorine-rich environments (eg swimming pool cover, ocean, sea) should be cautious.

General (uniform) corrosion
Full corrosion is so serious for stainless steel than other steels. It only occurs in stainless steel at pH <1.0. Should be mentioned in the table of the manufacturer's documentation, or the corrosion engineer's notice should be sought if the stainless steel is in contact with the chemical.

Intergranular corrosion and welding attenuation
When the austenitic stainless steel is heated between 450-850 and 0 ° C for a long time, the carbon in the steel diffuses into the grain boundary precipitates and chromium carbide. This eliminates the chromium content from the solid solution and leaves adjacent to the lower grain boundaries. Under this condition the steel is called "sensitized". Grain boundaries become easier for subsequent exposure prior to attack in a corrosive environment. When it occurs in the heat affected zone of the weldment, this phenomenon is called welding decay.

Stainless steel grades with low carbon content (~0.03%) are not sensitized by arc processes (for rapid heating and cooling), even for plates up to 20 mm in thickness. In addition, the modern steelmaking process means that the carbon content of 0.05% or less usually reaches the standard carbon grades 304 and 316, so these grades are not prone to welding by arc welding process.